EP0261704B1 - Process for producing phosphate coatings on metal surfaces - Google Patents

Process for producing phosphate coatings on metal surfaces Download PDF

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Publication number
EP0261704B1
EP0261704B1 EP87201520A EP87201520A EP0261704B1 EP 0261704 B1 EP0261704 B1 EP 0261704B1 EP 87201520 A EP87201520 A EP 87201520A EP 87201520 A EP87201520 A EP 87201520A EP 0261704 B1 EP0261704 B1 EP 0261704B1
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Prior art keywords
process according
contacted
phosphating solution
fluoride
aqueous phosphating
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German (de)
French (fr)
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EP0261704A1 (en
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Gisela Beege
Dieter Hauffe
Peter Dr. Mischke
Werner Dr. Rausch
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GEA Group AG
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Metallgesellschaft AG
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    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
    • C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
    • C23C22/34—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides
    • C23C22/36—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates
    • C23C22/362—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing fluorides or complex fluorides containing also phosphates containing also zinc cations
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C22/73—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals characterised by the process
    • C23C22/77—Controlling or regulating of the coating process

Definitions

  • the invention relates to a method for producing phosphate coatings on surfaces which are formed from aluminum or its alloys and at least one of the materials steel or galvanized steel, in spraying or spray-dipping by means of phosphating solutions containing zinc, phosphate, fluoride ions and accelerators, and its use as Preparation of the surfaces for electrocoating.
  • a normal zinc process is known from FR-A-2159181, in which metal surfaces from the group aluminum, iron, steel and zinc are brought into contact with phosphating solutions which contain zinc, phosphate, nitrate, nitrite and fluoride ions in such solutions
  • Quantities and ratios include that the free acid is 0.2 to 5 points and the total acid is at least 4 points.
  • the weight ratio of metal to phosphate should be set to at least 1: 1.
  • the preferred concentrations are between 0.7 and 6 g / l for zinc, between 1.0 and 20 g / l for phosphate and between 1.5 and 10 g / l for nitrate.
  • the object of the invention is to provide a method for producing phosphate coatings on surfaces which are formed from aluminum or its alloys and at least one of the materials steel or galvanized steel, which does not have the aforementioned disadvantages, in particular leads to uniform phosphate coatings and without effort is feasible with regard to the solution components and the procedure.
  • the partial surface consisting of aluminum materials to be treated by the method according to the invention comprises the pure metal and its alloys. Pure aluminum, AIMg and AIMgSi kneading materials may be mentioned as examples. A detailed description of the aluminum materials can be found e.g. in the aluminum paperback, 14th edition, aluminum publishing house, Düsseldorf, 1983.
  • the other partial area consists of steel and / or galvanized steel.
  • steel is understood to mean low-alloy steel, as it is e.g. in the form of sheets for body construction.
  • galvanized steel includes e.g. Galvanized and hot-dip galvanized and refers to zinc and zinc alloys, e.g. ZnNi, ZnFe, ZnAI.
  • the method according to the invention is used in spraying and splash immersion.
  • the spraying time must be at least as long as is necessary for an at least largely closed phosphate layer formation on the aluminum. This usually takes at least 60 seconds.
  • the required fluoride concentration corresponds approximately to the proportion of dissociated fluoride (F-) present in the phosphating solution.
  • F (el) value 80 to 220 mg / 1 at the usual bath pH values of the low-zinc phosphating baths, about 0.4 to 0.9 g / l NH 4 HF 2 or equivalent amounts of other simple must -Fluoride containing salts are added.
  • the bath is preferably supplemented by adding enough simple fluoride-containing salt to the bath until the desired measured value of F (el) is reached. At least part of the fluoride is added as single fluoride.
  • the phosphating solutions can also contain complex fluoride, e.g. of boron or silicon, contained in the amounts customary in phosphating technology. Any fluoride released by dissociation, which is also detected by the fluoride-sensitive electrode and is therefore contained in the setpoint to be set.
  • complex fluoride e.g. of boron or silicon
  • the low value in the brackets applies to low concentrations of P z 0 5 , the higher value for higher concentrations in the phosphating solution.
  • the correction element K takes into account the influence of the measured fluoride activity (F (el)) on the optimal free acid content.
  • F (el) is used in the dimension (mg / l).
  • F (el) is used in the dimension (mg / l).
  • 10 ml bath sample are diluted with approx. 100 ml deionized water and titrated with 0.1 N NaOH against the change from dimethyl yellow to a weak yellow color, which corresponds to a pH value of 4.25.
  • FS is equal in number to the ml of sodium hydroxide solution used.
  • the substances generally used in phosphating technology can be used as accelerators. It is particularly advantageous to bring the surface into contact with an aqueous phosphating solution, the accelerator being chlorate, bromate, nitrate, nitrite, peroxide and / or organic nitro compounds.
  • the accelerator being chlorate, bromate, nitrate, nitrite, peroxide and / or organic nitro compounds.
  • a particularly suitable organic nitro compound is meta-nitrobenzosulfonate. They are dosed in the usual quantities.
  • the phosphating bath temperature is usually chosen between 40 and 60 ° C and the spraying time between 1 and 3 minutes.
  • the phosphate layers produced by the process according to the invention have a weight per unit area of approximately 1 to 5 g / m 2 and can be used well in all areas in which phosphate coatings are used.
  • a particularly advantageous application is the preparation of the metal surfaces for painting.
  • the method can be used with particular advantage as preparation for the electrocoating process.

Description

Die Erfindung betrifft ein Verfahren zum Erzeugen von Phosphatüberzugen auf Oberflächen, die aus Aluminium oder dessen Legierungen sowie mindestens einem der Werkstoffe Stahl oder verzinktem Stahl gebildet werden, im Spritzen oder Spritztauchen mittels Zink-, Phosphat-, Fluoridionen und Beschleuniger enthaltenden Phosphatierungslösungen sowie dessen Anwendung als Vorbereitung der Oberflächen für die Elektrotauchlackierung.The invention relates to a method for producing phosphate coatings on surfaces which are formed from aluminum or its alloys and at least one of the materials steel or galvanized steel, in spraying or spray-dipping by means of phosphating solutions containing zinc, phosphate, fluoride ions and accelerators, and its use as Preparation of the surfaces for electrocoating.

Est ist bekannt, die Spritzphosphatierung von Metalloberflächen, die aus Aluminium und dessen Legierungen sowie Stahl und/oder verzinktem Stahl gebildet sind, Fluorid enthaltende Zinkphosphatlösungen einzusetzen. Diese Arbeitweise hat sich bei den sogenannten Normalzink-Verfahren mit Zinkgehalten in der Phosphatierungslösung von z.B. 2 bis 6 g/I gut bewährt.It is known to use the spray phosphating of metal surfaces, which are formed from aluminum and its alloys as well as steel and / or galvanized steel, with zinc phosphate solutions containing fluoride. This procedure has been used in the so-called normal zinc processes with zinc contents in the phosphating solution of e.g. Well proven 2 to 6 g / l.

Aus der FR-A-2159181 ist ein Normalzink-Verfahren bekannt, bei dem man Metalloberflächen aus der Gruppe Aluminium, Eisen, Stahl und Zink mit Phosphatierungslösungen in Kontakt bringt, die Zink-, Phosphat-, Nitrat-, Nitrit- und Fluoridionen in solchen Mengen und Verhältnissen enthalten, daß die freie Säure 0,2 bis 5 Punkte und die Gesamtsäure mindestens 4 Punkte betragen. Das Gewichtsverhältnis von Metall zu Phosphat soll dabei wenigstens auf 1:1 eingestellt sein. Die bevorzugten Konzentrationen liegen liegen für Zink zwischen 0,7 und 6 g/I, für Phosphat zwischen 1,0 und 20 g/I und für Nitrat zwischen 1,5 und 10 g/i.A normal zinc process is known from FR-A-2159181, in which metal surfaces from the group aluminum, iron, steel and zinc are brought into contact with phosphating solutions which contain zinc, phosphate, nitrate, nitrite and fluoride ions in such solutions Quantities and ratios include that the free acid is 0.2 to 5 points and the total acid is at least 4 points. The weight ratio of metal to phosphate should be set to at least 1: 1. The preferred concentrations are between 0.7 and 6 g / l for zinc, between 1.0 and 20 g / l for phosphate and between 1.5 and 10 g / l for nitrate.

Eine Übertragung dieser Arbeitsweise auf die sogenannte Niedrigzink-Phosphatierung im Spritzen, bei der mit Zinkhalten in der Phosphatierungslösung von unter 1 g/I gearbeitet wird, bereitete erhebliche Schwierigkeiten. Die Gleichmäßigkeit und Deckungsgrad der Phosphatschichten auf dem Aluminium unterliegen erheblichen Schwankungen, so daß eine befriedigende Anwendung dieser Arbeitweise in der Praxis nicht möglich ist.Transferring this procedure to the so-called low-zinc phosphating in spraying, in which zinc contents in the phosphating solution of less than 1 g / l are used, presented considerable difficulties. The uniformity and degree of coverage of the phosphate layers on the aluminum are subject to considerable fluctuations, so that a satisfactory application of this method of operation is not possible in practice.

Aufgabe der Erfindung ist es, ein Verfahren zur Erzeugung von Phosphatüberzügen auf Oberflächen, die aus Aluminium oder dessen Legierungen sowie mindestens einem der Werkstoffe Stahl oder verzinktem Stahl gebildet werden, bereitzustellen, das die vorgenannten Nachteile nicht aufweist, insbesondere zu gleichmäßigen Phosphatüberzügen führt und ohne Aufwand hinsichtlich der Lösungsbestandteile und der Verfahrensführung durchführbar ist.The object of the invention is to provide a method for producing phosphate coatings on surfaces which are formed from aluminum or its alloys and at least one of the materials steel or galvanized steel, which does not have the aforementioned disadvantages, in particular leads to uniform phosphate coatings and without effort is feasible with regard to the solution components and the procedure.

Die Aufgabe wird gelöst, indem das Verfahren der eingangs genannten Art entsprechend der Erfindung derart ausgestaltet wird, daß man die Oberflächen mit einer wäßrigen Phosphatierungslösung in Berührung bringt, die

  • 0,4 bis 0,8 g/I Zn
  • 10 bis 20 g/1 P205
  • mindestens eine Beschleuniger sowie
  • 80 bis 220 mg/I Fluorid ("F(el)", bestimmt durch eine in die Badlösung eingetauchte fluoridintensive Elektrode)
    enthält und in der der Gehalt an Freier Säure (FS) auf einen Wert entsprechend
    Figure imgb0001
    eingestellt ist und gehalten wird, wobei sich K gemäß
    Figure imgb0002
    errechnet.
The object is achieved by designing the method of the type mentioned at the outset in accordance with the invention in such a way that the surfaces are brought into contact with an aqueous phosphating solution which
  • 0.4 to 0.8 g / l Zn
  • 10 to 20 g / 1 P 2 0 5
  • at least one accelerator as well
  • 80 to 220 mg / l fluoride ("F (el)", determined by a fluoride-intensive electrode immersed in the bath solution)
    contains and in which the content of free acid (FS) to a value accordingly
    Figure imgb0001
     is set and held, with K according to
    Figure imgb0002
     calculated.

Die nach dem erfindungsgemäßen Verfahren zu behandelnde, aus Aluminium-Werkstoffen bestehende Teilfläche umfaßt das reine Metall und dessen Legierungen. Als Beispiele seien Reinaluminium-, AIMg und AIMgSi-Knetwerkstoffe genannt. Eine ausführliche Darstellung der Aluminiumwerkstoffe findet sich z.B. im Aluminium-Taschenbuch, 14. Auflage, Aluminium-Verlag, Düsseldorf, 1983.The partial surface consisting of aluminum materials to be treated by the method according to the invention comprises the pure metal and its alloys. Pure aluminum, AIMg and AIMgSi kneading materials may be mentioned as examples. A detailed description of the aluminum materials can be found e.g. in the aluminum paperback, 14th edition, aluminum publishing house, Düsseldorf, 1983.

Die weitere Teilfläche besteht aus Stahl und/oder verzinktem Stahl. Unter dem Begriff Stahl wird unbis niedriglegierter Stahl verstanden, wie er z.B. in Form von Blechen für den Karosseriebau Verwendung findet. Der Begriff verzinkter Stahl umfaßt z.B. Verzinkungen auf elektrolytischem und auf dem Schmelztauch-Wege und bezieht sich auf Zink und Zinklegierungen, z.B. ZnNi, ZnFe, ZnAI.The other partial area consists of steel and / or galvanized steel. The term steel is understood to mean low-alloy steel, as it is e.g. in the form of sheets for body construction. The term galvanized steel includes e.g. Galvanized and hot-dip galvanized and refers to zinc and zinc alloys, e.g. ZnNi, ZnFe, ZnAI.

Die Anwendung des erfindungsgemäßen Verfahrens erfolgt im Spritzen und Spritztauchen. Bei der letztgenannten Variante muß die Spritzzeit mindestens so lange sein, wie zu einer mindestens weitgehend geschlossenen Phosphatschichtausbildung auf dem Aluminium erforderlich ist. Überlicherweise sind hierfür mindestens 60 sec notwendig.The method according to the invention is used in spraying and splash immersion. In the latter variant, the spraying time must be at least as long as is necessary for an at least largely closed phosphate layer formation on the aluminum. This usually takes at least 60 seconds.

Die zu behandelnden Metalloberflächen müssen frei sein von störenden Belägen aus Ölen, Schmierstoffen, Oxiden und dergleichen, die eine einwandfreie Schichtbildung beeinträchtigen können. Hierzu werden die Oberflächen in geeigneter Weise gereinigt. Zur Unterstützung der Phosphatschichtbildung wird die Oberfläche vorzugsweise vor der Erzeugung des Phosphatüberzuges mit einem an sich bekannten Aktivierungsmittel, z.B. einer titanphosphathaltigen wäßrigen Suspension, aktiviert. Das Aktivierungsittel kann im Reinigerbad oder als getrennte Verfahrensstufe zum Einsatz kommen.The metal surfaces to be treated must be free from disruptive deposits of oils, lubricants, oxides and the like, which can impair proper layer formation. For this purpose, the surfaces are cleaned in a suitable manner. In order to support the formation of the phosphate layer, the surface is preferably coated before the phosphate coating is produced an activating agent known per se, for example an aqueous suspension containing titanium phosphate. The activating agent can be used in the cleaning bath or as a separate process step.

Die Einhaltung der Konzentrationen an Zink und P205 ist ausschlaggebend für die Erzeugung von qualitativ hochwertigen Phosphatüberzügen. Bei Unterschreitung der Konzentrationen werden die Schichten ungleichmäßig. Insbesondere nimmt ihre Eignung als Vorbereitung für die Lackierung ab. Bei Überschreitung der Grenzwerte vermindert sich ebenfalls die Qualität in Verbindung mit einer Lackierung, während der visuelle Eindruck weiterhin gut bleibt.Compliance with the concentrations of zinc and P 2 0 5 is crucial for the production of high quality phosphate coatings. If the concentrations are undershot, the layers become uneven. In particular, their suitability as preparation for painting decreases. If the limit values are exceeded, the quality in connection with painting is also reduced, while the visual impression remains good.

Die geforderte und mit der fluoridsensitiven Elektrode erfaßte Konzentration an Fluorid entspricht etwa dem in der Phosphatierungslösung vorliegenden Anteil an dissoziiertem Fluorid (F-). Um einen F(el)-Wert von 80 bis 220 mg/1 bei den üblichen Bad-pH-Werten der Niedrigzink-Phosphatierbäder einzustellen, müssen etwa 0,4 bis 0,9 g/I NH4HF2 oder äquivalente Mengen anderer Einfach-Fluorid enthaltender Salze zugegeben werden. Die Badergänzung erfolgt vorzugsweise so, daß man dem Bad so viel Einfach-Fluorid enthaltendes Salz zusetzt, bis der gewünschte Meßwert von F(el) erreicht ist. Mindestens ein Teil des Fluorides wird als Einfach-Fluorid zugesetzt.The required fluoride concentration, measured with the fluoride-sensitive electrode, corresponds approximately to the proportion of dissociated fluoride (F-) present in the phosphating solution. In order to set an F (el) value of 80 to 220 mg / 1 at the usual bath pH values of the low-zinc phosphating baths, about 0.4 to 0.9 g / l NH 4 HF 2 or equivalent amounts of other simple must -Fluoride containing salts are added. The bath is preferably supplemented by adding enough simple fluoride-containing salt to the bath until the desired measured value of F (el) is reached. At least part of the fluoride is added as single fluoride.

Zusätzlich zum Einfach-Fluorid können die Phosphatierungslösungen auch komplexes Fluorid, z.B. von Bor oder Silizium, in den in der Phosphatiertechnik üblichen Mengen enthalten. Durch Dissoziation gegebenenfalls freigesetztes Fluorid worin von der fluoridsensitiven Elektrode ebenfalls erfaßt und ist mithin im einzustellenden Sollwert enthalten.In addition to single fluoride, the phosphating solutions can also contain complex fluoride, e.g. of boron or silicon, contained in the amounts customary in phosphating technology. Any fluoride released by dissociation, which is also detected by the fluoride-sensitive electrode and is therefore contained in the setpoint to be set.

Die Grenzen für den mit der fluoridsensitiven Elektrode erfaßten Fluoridgehalt sind von wesentlicher Bedeutung. Wenn die Grenze für F(el) von 80 mg/I unterschritten wird, reicht der Beizangriff der Phosphatierungslösung nicht aus, um gleichmäßig deckende Phosphatschichten zu erzeugen. Bei Überschreitung der Obergrenze von F(el) = 220 mg/I wird eine ordnungsgemäße Phosphatschichtausbildung durch den parallel ablaufenden zu hohen Beizangriff gestört.The limits for the fluoride content measured with the fluoride-sensitive electrode are of essential importance. If the limit for F (el) falls below 80 mg / I, the pickling attack of the phosphating solution is not sufficient to produce uniformly covering phosphate layers. If the upper limit of F (el) = 220 mg / I is exceeded, proper formation of the phosphate layer is disrupted by the excessive pickling attack which runs in parallel.

Die richtige Einstellung der Freien Säure (FS) in der Phosphatierungslösung ist von wesentlicher Bedeutung fü die Art der Ausbildung des Phosphatüberzuges. Grundsätzlich ist zu sagen, daß in den im erfindungsgemäßen Verfahren zum Einsatz kommenden Phosphatierungslösung die Freie Säure deutlich höher liegt als in den korrespondierenden fluoridfreien Phosphatierungslösung. Versucht man, nach Zugabe von Fluorid, den gewohnten Wert für die Freie Säure vor der Zugabe aufrechtzuerhalten, so findet eine schnelle Abnahme der Zinkkonzentration statt und die Qualität der erzeugten Schichten verschlechtert sich.The correct setting of the free acid (FS) in the phosphating solution is essential for the type of formation of the phosphate coating. Basically, it can be said that in the phosphating solution used in the process according to the invention the free acid is significantly higher than in the corresponding fluoride-free phosphating solution. If one tries to maintain the usual free acid value after the addition of fluoride, the zinc concentration decreases rapidly and the quality of the layers produced deteriorates.

In der Beziehung für den einzustellenden FS-Wert gilt der niedrige Wert in der Klammer für niedrige Konzentrationen an Pz05, der höhere Wert für höhere Konzentrationen in der Phosphatierungslösung. Das Korrekturglied K berücksichtigt den Einfluß der gemessenen Fluoridaktivität (F(el)) auf den optimalen Gehalt an Freier Säure.In the relationship for the FS value to be set, the low value in the brackets applies to low concentrations of P z 0 5 , the higher value for higher concentrations in the phosphating solution. The correction element K takes into account the influence of the measured fluoride activity (F (el)) on the optimal free acid content.

Bei der Ermittlung des Korrekturgliedes Wird F(el) in der Dimension (mg/l) eingesetzt. Zur Bestimmumg der Freien Säure (FS) werden 10 ml Badprobe mit ca. 100 ml vollentsalztem Wasser verdünnt und mit 0,1 n NaOH gegen den Umschlag von Dimethylgelb auf schwache Gelbfärbung, die etwa einem pH-Wert von 4,25 entspricht, titriert. FS ist zahlengleich den verbrauchten ml an Natronlauge.When determining the correction element, F (el) is used in the dimension (mg / l). To determine the free acidity (FS), 10 ml bath sample are diluted with approx. 100 ml deionized water and titrated with 0.1 N NaOH against the change from dimethyl yellow to a weak yellow color, which corresponds to a pH value of 4.25. FS is equal in number to the ml of sodium hydroxide solution used.

Besonders günstige Ergebnisse hinsichtlich der Qualität des erzeugten Phosphatüberzuges werden erhalten, wenn entsprechend eine bevorzugten Ausgestaltung der Erfindung die Metalloberfläche mit einer Phosphatierungslösung in Berührung gebracht wird, in der die Freie Säure (FS) auf einen Wert entsprechend

Figure imgb0003
eingestellt ist und gehalten wird. Hierbei zeigt sich, daß der einzustellende Gehalt an Freier Säure in einer unmittelbaren Beziehung zur P2O5-Konzentration (Cp2p5) steht. Eine nochmalige Verbesserung der Ergebnisse läßt sich erreichen, wenn man gemäß einer weiteren vorteilhaften Ausführungsform der Erfindung die Oberfläche mit einer Phosphatierungslösung in Berührung bringt, in der sich der Gehalt an Freier Säure (FS) gemäß
Figure imgb0004
errechnet.Particularly favorable results with regard to the quality of the phosphate coating produced are obtained if, according to a preferred embodiment of the invention, the metal surface is brought into contact with a phosphating solution in which the free acid (FS) corresponds to a value
Figure imgb0003
 is set and held. It shows that the free acid content to be set is directly related to the P 2 O 5 concentration (Cp 2 p 5 ). A further improvement in the results can be achieved if, according to a further advantageous embodiment of the invention, the surface is brought into contact with a phosphating solution in which the free acid content (FS) is in accordance with
Figure imgb0004
 calculated.

Als Beschleuniger können die in der Phosphatierungstechnik generell üblichen Substanzen verwendet werden. Von besonderem Vorteil ist es, die Oberfläche mit einer wäßrigen Phosphatierungslösung in Berührung zu bringen, die als Beschleuniger Chlorat, Bromat, Nitrat, Nitrit, Peroxid und/oder organische Nitroverbindungen. Eine besonderes geeignete organische Nitroverbindung ist meta-Nitrobenzosulfonat. Ihre Dosierung erfolgt in den üblichen Mengen.The substances generally used in phosphating technology can be used as accelerators. It is particularly advantageous to bring the surface into contact with an aqueous phosphating solution, the accelerator being chlorate, bromate, nitrate, nitrite, peroxide and / or organic nitro compounds. A particularly suitable organic nitro compound is meta-nitrobenzosulfonate. They are dosed in the usual quantities.

Eine weitere zweckmäßige Ausfuhrungsform der Erfindung sieht vor, die Phosphatüberzüge zu erzeugen, indem man die Oberflächen mit einer wäßrigen Phosphatierungslösung in Berührung bringt, die zusätzlich ein oder mehrere Kationen aus der Gruppe Ni, Mn, Mg, Ca aufweisen. Die Phosphatierungslösungen sollten die vorgenannten Kationen in Mengen von 0,1 bis 1,5 g/I enthalten. Diese Kationen werden zum Teil mit in die Phosphatschicht eingebaut und können unter speziellen Bedingungen zu einer Verbesserung der Schichtqualität führen.Another expedient embodiment of the invention provides for the phosphate coatings to be produced by bringing the surfaces into contact with an aqueous phosphating solution which additionally has one or more cations from the group Ni, Mn, Mg, Ca. The phosphating solutions should contain the aforementioned cations in amounts of 0.1 to 1.5 g / l. Some of these cations are built into the phosphate layer and, under special conditions, can lead to an improvement in the layer quality.

Die Phosphatierungslösungen können noch weitere, in der Phosphatiertechnik bekannte Zusätze zur Modifizierung der Verfahrensweise und der Schichteigenschaften enthalten. Als Beispiele seien genannt: Tenside, Polyhydroxycarbonsäuren, Polyphosphate, Ammonium-, Alkali-, Kupfer-, Kobaltionen und indifferente Anionen, wie Chlorid und Sulfat.The phosphating solutions can also contain further additives known in phosphating technology for modifying the procedure and the layer properties. Examples include: surfactants, polyhydroxycarboxylic acids, polyphosphates, ammonium, alkali, copper, cobalt ions and indifferent anions such as chloride and sulfate.

Die Phosphatierbadtemperatur wird üblicherweise zwischen 40 und 60°C und die Spritzzeit zwischen 1 und 3 min gewählt.The phosphating bath temperature is usually chosen between 40 and 60 ° C and the spraying time between 1 and 3 minutes.

Die mit dem erfindungsgemäßen Verfahren erzeugten Phosphatschichten besitzen ein Flächengewicht von etwa 1 bis 5 g/m2 und sind auf allen Gebieten, auf denen Phosphatüberzüge eingesetzt werden, gut einsetzbar. Ein besonders vorteilhafter Anwendungsfall liegt in der Vorbereitung der Metalloberflächen für die Lackierung. Als Vorbereitung für die Elektrotauchlackierung ist das Verfahren mit besonderem Vorteil anwendbar.The phosphate layers produced by the process according to the invention have a weight per unit area of approximately 1 to 5 g / m 2 and can be used well in all areas in which phosphate coatings are used. A particularly advantageous application is the preparation of the metal surfaces for painting. The method can be used with particular advantage as preparation for the electrocoating process.

Die Erfindung wird anhand der folgenden Beispiele näher und beispielsweise erläutert:The invention is explained in more detail and, for example, using the following examples:

BeispieleExamples

Vier Serien von Verbundblechen mit Oberflächen aus AIMg3 und Stahl, AIMg3 und verzinktem Stahl, AIMgO, 4Sil, 2 und Stahl sowie AIMgO, 4Sii!, 2 und verzinktem Stahl wurden mit einem aktivierenden mildalkalischen Reiniger 2 min bei 50°C spritzentfettet, anschließend mit Wasser gespült und danach 2 min mit folgenden Phosphatierungslösungen im Spritzen phosphatiert:

Figure imgb0005
Four series of composite sheets with surfaces made of AIMg3 and steel, AIMg3 and galvanized steel, AIMgO, 4Sil, 2 and steel as well as AIMgO, 4Sii !, 2 and galvanized steel were spray degreased with an activating mildly alkaline cleaner for 2 min at 50 ° C, then with water rinsed and then phosphated in the spray with the following phosphating solutions for 2 min:
Figure imgb0005

Nach der Phosphatierung wurde mit Wasser gespült, mit Cr(VI)-haltigem Passivierungsmittel nachgespült, mit vollentsalztem Wasser abgebraust und getrocknet.After the phosphating, rinsing with water, rinsing with Cr (VI) -containing passivating agent, rinsing with demineralized water and drying.

Auf allen vier Blechserien wurden mit sämtlichen Phosphatiervarianten A, B und C gleichmäßig deckende Phosphatischichten erzeugt, die sich gut für eine anschließende Elektrotauchlackierung eigneten.With all phosphating variants A, B and C, uniformly opaque phosphate layers were produced on all four sheet metal series, which were well suited for subsequent electrocoating.

Claims (9)

1. A process of producing phosphate coatings on surfaces which consist of aluminium or its alloys and of at least one of the materials steel and galvanised steel by spraying or by spray/dipping with phosphating solutions which contain zinc ions, phosphate ions, fluoride ions and accelerator, characterized in that the surfaces are contacted with an aqueous phosphating solution which contains
0.4 to 0.8 g/I Zn
10 to 20 g/I P205
at least one accelerator and
80 to 220 mg/I fluoride ("F(el)")
as determined by a fluoride-sensitive electrode immersed into the bath solution and in which the content of free acid (FA) (in points) has been adjusted to and is maintained at a value corresponding to
Figure imgb0014
Figure imgb0015
2. A process according to claim 1, characterized in that the surfaces are contacted with an aqueous phosphating solution in which the content of free acid (FA) has been adjusted to and is maintained at a value corresponding to
Figure imgb0016
3. A process according to claim 1 or 2, characterized in that the surfaces are contacted with an aqueous phosphating solution in which the content of free (FA) acid is determined with
Figure imgb0017
4. A process according to claim 1, 2 or 3, characterized in that the surfaces are contacted with an aqueous phosphating solution which contains an accelerator consisting of chlorate, bromate, nitrate, nitrite, peroxide and/or an organic nitro compound.
5. A process according to claim 1 to 4, characterized in that the surfaces are contacted with an aqueous phosphating solution which contains meta-nitrobenzene sulfonate as organic nitro compound.
6. A process according to any of claimss 1 to 5, characterized in that the surfaces are contacted with an aqueous phosphating solution which additionally contains one or more cations of the group Ni, Mn, Mg, Ca.
7. A process according to claim 6, characterized in that the surfaces are contacted with an aqueous phosphating solution which contains the cations of the group Ni, Mn, Mg, Ca in an amount of 0.1 to 1.5 g/I.
8. The use of the process according to any of the claims 1 to 7 in preparing the surfaces for being painted.
7. The use of the process according to claim 8 in preparing the surfaces for being electro immersion painted.
EP87201520A 1986-09-18 1987-08-11 Process for producing phosphate coatings on metal surfaces Expired - Lifetime EP0261704B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE3631759 1986-09-18
DE19863631759 DE3631759A1 (en) 1986-09-18 1986-09-18 METHOD FOR PRODUCING PHOSPHATE COATINGS ON METAL SURFACES

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EP0261704A1 EP0261704A1 (en) 1988-03-30
EP0261704B1 true EP0261704B1 (en) 1991-01-23

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JP (1) JP2604387B2 (en)
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DE (2) DE3631759A1 (en)
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EP0261704A1 (en) 1988-03-30
GB2195359B (en) 1990-06-27
CA1308338C (en) 1992-10-06
DE3767631D1 (en) 1991-02-28
GB2195359A (en) 1988-04-07
GB8722064D0 (en) 1987-10-28
ES2020259B3 (en) 1991-08-01
US4849031A (en) 1989-07-18
DE3631759A1 (en) 1988-03-31
JPS63157879A (en) 1988-06-30
JP2604387B2 (en) 1997-04-30

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